The present invention relates to a thermostat comprising a bimetal switch element reacting at selected temperatures which on one of its ends is fastened on a frame and on its other end is provided with an electric contact adapted to engage a fixed contact provided on the frame.
As thus described, such a thermostat is generally known.
Usually in thermostats a bimetal switch element is used as a temperature sensing member. This switch element is moveable in dependence on the ambient temperature either with continuous creep movement or with snap-action. The bimetal itself can conduct a current in the electric circuit. In dependence on the selfheating of the switch element by such current, the thermostat can also be current responsive. Said current sensibility can be increased by applying additional heating means on the thermostat. The switching time is highly influenced by the heat mass and heat transfer in the thermostat and, of course, also by the temperature at which the switch element will open or close the electric circuit in which the thermostat is incorporated.
Since it is easier to add mass to the thermostat than remove mass both for the fixed thermostat function and the current sensing function, a light mass is usually desirable. However, the risk of permanent deformations during manufacture, adjustment and use of the thermostat is increased thereby.
Frequently upon manufacture of said thermostat, differences in materials and dimesions will cause an inaccurate circuit response, said inaccuracies being difficult to correct. The larger the number of parts of the thermostat, the harder said correction will be.
Usually for this kind of thermostat a large number of model types is also required. Such models differ not only with respect to the desired switch operating temperature and with respect to the various sensibilities to temperature and current of the bimetal and the overall thermostat, but also with respect to the mechanical differences in the connecting terminals in the electric circuit.
This makes an accurate structure more difficult too.